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TREATING TIMBER WITH PRESERVATIVE FLUIDS.

77117255296 Xfl v N. PETEns. Phulwhlhogmpllnn Washinglnn. n. c.

2 Sheets-Sheet 2.

(No Model.)

S. B. BOULTON.

TREATING TIMBER WITH PRESERVATLVE FLUIDS.

No. 247,602. Patented Sept. 27,1881.

UNITED STATES PATENT OFFIcE. "T

SAMUEL vB. BOULTON, OF OOPPED HALL, COUNTY OFHERTFORD, ENGLAND.

TREATING TIMBER WITH PRESERVATIVE FLUID-S.

SPECIFICATION forming part of Letters Patent No. 247,602, dated September 27, 1881.

- Application filed April 19, 1881. '(No specimens.) Patented in England May 15, 1879.

To allwhom it may concern Beit known that I, SAMUEL BAGSTER BOUL TON, a citizen of England, residing at ()opped Ha1l,in the county of Hertford", England, have 5 invented an Improvement; in Treating Timber with Antiseptic or'Preservative Fluids, (for which I have obtained a Patent in Great Britain, No. 1,954, hearing date May 15, 1879,) of which the following is a specification;

In treating. timber with antiseptic or preservative fluids-such as the heavy oils of tar,

commonly called creosote, or other oily or servativefluid is introduced into the vessel. The

exhaust having been stopped, heat and press: 3 5 ure are then applied to the contents of the vessel in order to force the fluid into the timber. According to another process which has been sometimes employed the timber is merely steepedin the preservative fluid heated in open tanks. By this last process the impregnation has-been found to be very imperfect.

In the first-named process as little, or practically none, of the moisture contained in the wood is got rid of by the air-exhausting oper- 3 ration, while during the subsequent impregnation under pressure any such removal of the moisture is impossible, previous drying in the open air for a considerable length of time has to be resorted to, entailinga great loss of time 40 and only effecting the drying imperfectly; or

artificial methods of desiccation have been em.-

.ployed-such as by heatin g the timber by steam 'or currents of hot air-which methods, however, have been found to be open to many prac- 5 tical objections, such as the deterioration of.

the timber.

My present invention has for its object to obviatethe loss of time, and also the labor and expense, andother inconveniences attendant upon drying the timber by the methods above described before. subjecting it to the action of the creosote, and also to enable a greater amount of moisture to be expelled from the timber than can be extracted either by lengthened drying in the open air or by the process of steeping in open tanks. Ithusinsureamore perfect saturation with the creosote. For'this purpose I avail myself 'of the fact that moisture can be effectually evaporated from substances at a much lower temperature than is possible under atmospheric pressure if they-are heated under a partial vacuum, the necessary amount of heat for expelling a certain quantity of moisture being less in proportion as the pressure is diminished.

Accordingly, my invention consists in applying heat to the timber inside a closed vessel in which a partial vacuum is continuously maintained by means of an air-pump and condenser for drawing off and condensing the watery va- 70 per as it is given off from the wood, the heat being applied through the medium of the antiseptic fluid itself, with which the timber is to be impregnated. Any convenient form of apparatus may be used for this process, but I generally make use of the well-known pressure tank or cylinder and apparatus, but with the modifications hereinafter described.

The timber having been'introduced into the cylinder, which is then hermetically closed, a communication is opened with the air-pump, and a sufficient vacuum may be produced in the usualway in order to facilitate the entry of the creosote into the cylinder, but this preliminary vacuum is not necessary to my process." The creosote being introduced into the cylinder, I take advantage of the fact that the creosote or other heavy oil has a much higher point of ebullition and evaporation than the boiling-point of water, so that although the heating may be carried considerably over 212 Fahrenheit in order to accelerate the evaporating process, there will be little or no vapor of creosote given 011'. The heating and evaporation can, however, becarried on effectually at a considerably lower temperature, owing to the partial vacuum maintained in the cylinder, although, in order to accelerate the process, the creosote may be heated to a temperature of from 250 to 300 Fahrenheit, or even higher, without arriving at the distilling-point of the creosote. In most'cases I prefer, however, to use a temperature not much exceeding 212, or even lower, so as to prevent any deterioration ot the timber. The timber being thus subjected to a temperature which will evaporate the watery particles contained in it, but not the creosote, I draw oft the watery vapor thus produced by means of an air-pump which communicates by a pipe or pipes with one or more air-chambers situated on the top of the cylinder. A condenser or worm is interposed between the said air-chamber and the air-pump, so that the steam and any oily pan ticles which may accompany it are condensed, and the latter may be separated and recovered. It will thus be seen that by my above-described invention the watery particles contained in the timber are subjected to a process of distillation by the heat of the creosote in which it is submerged, assisted by the action of the airpump and condenser, and the cells of the wood, being expanded by the heat and the escape of vapor, become better adapted for the reception of the antiseptic fluid which enters the wood and takes the place of the evacuated moisture. 1f considerable heat within the above-named limits be applied, a large quantity of creosote will be found to have been absorbed by the wood, so that the process may in certain cases end here, or it may be supplemented by forcing in further quantities of creosote by the action of theforce-pump, according to the well-known method or this second part of the process may be carried out and the supplemental quantity of creosote forced into the wood by substituting for the action of the ordinary forcepump thepressure of steam, gas, orcompressed air, as pointed out in the specification to my English patent of 16th March, 1865, No. 734.

It will be seen that by the above process 1 am enabled to treat the wood while still green or saturated with sap or moisture, and in the case of floated timber to take it direct from the water, and to effect the removal of such moisture and the saturation with creosote in one and the same "essel in a comparatively short space of time and in a more perfect manner than heretofore.

The heating of the creosote may be etfected either by steam-pipes inside the creosotingvessel, (in which case the steam may with advantage be superheated before being introduced therein,) or by fire-heat applied externally thereto, or the creosote may be heated to the required degree before being introduced into the cylinder. For this last purpose I preferto provide near the creosoting-vessel a separate closed receptacle, communicating therewith by means of pipes so arranged that the creosote can circulate freely through both vessels, and 1 apply heat to the said separate receptaele, either by a fire or by a steam-coil, so as to maintain the circulating creosote at the desired temperature as long as may be necessary.

Figureloftheaecompanyingdrawingsshows, by way of example, a part sectional elevation of one arrangement of combined apparatus for carrying out my invention, in which the heating of the antiseptic fluid is effected by steampipes. A is the creosoting-cylinder, into which the timber B is charged through the end A, capable of being closed hermetically by adoor or cover, in the usual manner. 0 are steampipes, into which steam is conducted from any suitable generator, being, by preference, previously superheated in a superheater, 0. From the dome A of the cylinder A an exhaust-pipe passes to the condensing-worm E, com municating with the receiver F, which, in its turn, is in connection with the exhaust-pumps Gr, worked by any convenient motor-engine. The cylin- (ler A, having been charged with the timber, is closed hermetically. The antiseptic fluid is made to enter it, either by drawing it in from a tank, H, through a pipe, I, provided with a stop-cock, the cylinder being exhausted by the air-pumps Gfor this purpose, or the fluid may be introduced in any other convenient manner. The contents of the cylinder being nowheated by the steam-pipes, the watery vapor given 011' from the wood is drawn otl'by the air-pumps,and becoming condensed on its passage through the worm E, the resulting liquid flows into the receiver F, while the uncondensed vapor and air are drawn off by the pumps. The liquid is discharged from time to time from the re ceiver F, through a pipe, F, provided with a stop-cock, into a tank, K, the height of the liquid in the receiver being indicated bya gage, F On completion of the heating process, pressure may, if necessary, be applied to the contents of the cylinder to complete the impregnation, as hereinbefore described, whereupon the fluid is discharged from the cylinder and the timber is removed. M M are pressure and vacuum gages for indicating the pressure and vacuum, respectively, in the cylinder A and receiver F.

Fig. 2 shows a part sectional elevation of the same combination of apparatus described with reference to Fig. 1, with the exception that the heating of the antiseptic fluid is effected by fire-heat in a separate vessel, L,com municating with the cylinder A by pipes L L, through which the fluids circulate continuously from the one vessel to the other. The other IIO parts are designated by the same letters of reference as in the previous arrangement, and need not be further described.

Although I prefer to effect the removal of the moisture from the timber entirely through the medium of the heated antiseptic fluid, as described, yet it will be evident that heat might be applied to the cylinder after the timber has been introduced and before the fluid is admitted, so as to first drive off a certain amount of moisture by this means, under maintenance of a partial vacuum by the air-pump and condenser, and then to complete the operation in the manner above described.

I am aware that timber has heretofore been impregnated with liquid-creosote vapors, but such a high degree of heat is essential to vaporize the creosote as to be very detrimental to the timberbeing treated; and, further, such process has not heretoforebeen carried on while the wood to be treated is contained in a vessel under continuous exhaustion.

I am also aware that it is not new to impregnate timber with liquid bituminous substances by first heating and drying in an oven, then placing the wood in a vessel containing the bituminous substance and exhausting the air from said vessel by means of a pump. In this process the heating of the wood in an oven is exceedin gly' objectionable, because the wood will become charred unless great care is exercised in controlling the heat.

I am also aware that timber has been boiled in a bath of creosote or coal-tar, the temperature of which is maintained at or near the boiling-point long enough to convert into steam and expel the watery constituents of the sap, which, with the vapor distilled from the boiling creosote, is received and condensed ina condenser for the purpose of separating the hydrocarbon and watery liquids by decantation. Such, not being my invention, is hereby disclaimed.

I claim in respect of the treatment of wood by antiseptic or preservative fluidsl. The method of heating timber with antiseptic or preservative fluids, by placing the timber in an undried condition in closed vessels, in which the watery particles are distilled or expelled from the wood by means of the heated creosote, or similar antiseptic liquid, with which the wood is to be impregnated, the resulting steam and other vapors being con tinuously exhausted from the vessel and condensed as they are generated.

2. The process herein described of treating timber, the same consisting in subjecting the timber, in a closed vessel under continuous exhaustion, to the action of creosote or other bituminous liquid heated to a temperature of 212 Fahrenheit, or more, but of a temperature below that at which the said liquid will vaporize, whereby the heated liquid serves to distill or vaporize the moisture in the timber, and such vapor is continuously exhausted from the vesso], as set forth. 

